fix signed warning errors in unittests

src/processor/minidump_processor_unittest.cc

Index: src/processor/minidump_processor_unittest.cc
diff --git a/src/processor/minidump_processor_unittest.cc b/src/processor/minidump_processor_unittest.cc
index 609a2a68039ad250393a5c563275ddd12f77858e..d43c1fc97a7e59073eaf967ed6db284d45a216a2 100644
--- a/src/processor/minidump_processor_unittest.cc
+++ b/src/processor/minidump_processor_unittest.cc
@@ -414,7 +414,7 @@ TEST_F(MinidumpProcessorTest, TestBasicProcessing) {
   ASSERT_EQ(state.crash_reason(), "EXCEPTION_ACCESS_VIOLATION_WRITE");
   ASSERT_EQ(state.crash_address(), 0x45U);
   ASSERT_EQ(state.threads()->size(), size_t(1));
-  EXPECT_EQ((*state.threads())[0]->tid(), 3060);
+  EXPECT_EQ((*state.threads())[0]->tid(), 3060U);
   ASSERT_EQ(state.requesting_thread(), 0);
   EXPECT_EQ(1171480435U, state.time_date_stamp());
   EXPECT_EQ(1171480435U, state.process_create_time());